Northern Sacramento Valley Branch Meeting - Land Subsidence in the Northern Sacramento Valley

The Northern Sacramento Valley Branch is pleased to present:


"Land Subsidence in the Northern Sacramento Valley"

 Presented By:

Bill Ehorn, P.G, CHG
Supervising Engineering Geologist, Northern Region Office

Department of Water Resources, Red Bluff, California



Land subsidence in the Northern Sacramento Valley has been monitored by extensometers, GPS surveys, CORS (active geodetic control), and Insar.   The monitoring began with extensometers in the early 2000’s followed by GPS subsidence networks in 2004 and 2008.  Most recently, CORS and NASA Insar subsidence data are available.  These measurement methods cover different parts of the valley and have differing degrees of accuracy ranging from 0.005 feet to 1-2 feet.  Records indicate that inelastic subsidence has not been measured in the Northern Sacramento Valley until the recent drought California had.  Below average precipitation amounts between 2011 and 2015, including two critical dry years, led to increased groundwater pumping and record low groundwater levels.  As a result, land subsidence has been measured in areas within Glenn and Colusa counties where large groundwater depressions exist on the west side of the valley.   The Sustainable Groundwater Management Act (SGMA) recognizes land subsidence as one of the six undesirable results and monitoring and reporting of land subsidence is required.  Additional efforts by the Department of Water Resources and local agencies have begun.     



Bill Ehorn, P.G, CHG is a supervising engineering geologist and the Regional Planning Branch Chief for DWR’s Northern Region Office. His primary responsibilities are supervising the Groundwater and Geologic Investigation, Data Collection and Management, Program Coordination, and the Land and Water Use sections. Bill began his career with DWR in 1990 as a Geology Graduate Student. After working as a geologist for six years in the private sector across Oregon and Washington and performing two years of stream gaging for DWR, he became a full-time Engineering Geologist for DWR in 1999. His experience includes well drilling and installation, aquifer characterization, data collection and management, conjunctive use planning and managing, groundwater quality assessments, groundwater modeling, and drought water banking. Bill has served as the supervisor of both the Groundwater and Geologic Investigations and the Data Collection and Management Sections. His recent work includes leading and directing Northern Region work associated with the sustainable groundwater management program.  He also assists with statewide integrated water resource planning and management.  Bill received his Bachelor‘s Degree in Physical Geography from the University of California at Santa Barbara in 1987 and a Master’s Degree in Hydrogeology from Chico State University in 1991.  He is a California and Oregon licensed Professional Geologist and a California Certified Hydrogeologist.  Bill’s hobbies include skiing, surfing, hunting, fishing, and flying airplanes.



Enviro-Tech Services Company began in 1987 as a small business enterprise designed to provide quality environmental products for purchase or rental. Enviro-Tech was started by a Geologist with a background in petroleum exploration, mining, and environmental consulting, therefore, the company is structured to respond swiftly to the product needs of the working field professional. We are a streamline and efficient operation with an experienced staff. Our clients receive a level of personal service unparalleled in the industry.


5:00 – 6:00 – No-Host Social and Registration
6:00 – 6:30 – Dinner and Announcements
6:30 – 7:30 – Keynote Speaker
7:30 – 8:00 – Questions and Answers







Members & Non-Members: $20.00
Students: $10.00

Questions about the meeting or to contact the Northern Sacramento Valley Branch in general, including submittal of your ideas and/or desires for future presentations, please contact Eddy Teasdale at


Thursday, May 4:  Helen E. Dahlke, Ph.D.
Integrated Hydrologic Sciences, Department of Land, Air and Water Resources
University of California, Davis
"Potential of Using Agricultural Fields for Groundwater Recharge: Soil Water Balance, Crop Suitability and Surface Water Availability"



GRA's Northern Sacramento Valley Branch is interested in supporting university science students. Our Scholastic Sponsorship Program is an opportunity to publicize your business while contributing toward a good cause. Your sponsorship will be acknowledged in the announcement, at the meeting, and space will be provided for a small display and brochures. Please contact Eddy Teasdale at for details.


Thu, March 9, 2017
5:00 p.m. - 8:30 p.m.

Event has ended


Casa Ramos Mexican Restaurant
2490 Fair Street
Chico, California 95928